Prompt user when Back button is pressed

Question

Which is the good place to ask user, whether (s)he wants to exit the app when (s)he clicked the back button? I considered the onPause and onStop, but t

Answer 1

This is a rather old question but it ranks high on Google so I figured it could need an Update:

@Override
public void onBackPressed() {
    AlertDialog.Builder builder = new AlertDialog.Builder(this);
    builder.setMessage("Do you want to exit the app?");

    // if user presses "Exit", then he is allowed to exit from application
    builder.setPositiveButton("Exit", (dialog, which) -> finish());

    // if user selects "Stay", just cancel this dialog and continue with app
    builder.setNegativeButton("Stay", (dialog, which) -> dialog.cancel());

    builder.create().show();
}